Shakespeare knew it, when he gave "this sceptered isle" to John of Gaunt's dying breath. Great artists knew it when they took their easels to the summit of our hills and captured England's finest landscapes. Soldiers knew it, when wartime propaganda urged victory to protect the countryside we love.The London Olympic designers knew it, when their opening ceremony defined our modern nation with pastoral scenes. Hell, even the government knows it. New official posters promoting Britain remind tourists that our "countryside is great".

Everyone knows it. The countryside is integral to the definition of Britain. It is indelibly part our heritage. It is a national asset that should be prized. So why are we so criminally casual about its loss?

The vandalism of rural Britain isn't happening with ordered precision. Each year, an area of countryside the size of Southampton is covered with concrete. But we aren't building inspiring new towns or green cities.

No, this loss is horribly random. Dismal, identikit developments disfigure historic market towns. Precious green spaces between villages are thoughtlessly destroyed. We are told not to worry, that only a few percentage points of countryside will be lost. The reality is that, outside of protected landscapes like national parks, the effective ruination of countryside and tranquillity is far greater.

England saw once before what random development would mean for the countryside. The great construction of the 1930s, which created millions of new homes, finally alarmed politicians when they saw that the suburban sprawl would not stop. The Town and Country Planning Act 1947 was brought in to end the era of unplanned development.

Ministers invoke that halcyon period of housing boom as an easy route once again out of recession, yet they forget the emergency action that followed. And that was in an era before mass ownership of cars. Today, simply relaxing planning controls wouldn't just see creeping suburbia: it would allow random development on any countryside that someone would sell.

Yes, planning controls drive up prices; yes, we once again have a housing shortage, and, yes, homes have never been so unaffordable. We do need to lower prices and rents. We should want to extend opportunity and enable young people to realise their dreams of ownership.

But this requires fundamental planning reform, not ill-thought relaxation of controls that were introduced for good reason. Gordon Brown tried and failed to push the system to construct more, but his top-down regional housing targets built only resentment. The new government heralded a localist approach, where communities would be given both the power and the responsibility to plan for development.

But even before the legislation was passed, ministers were spooked by an extended downturn and lost faith that their fledgling reforms would deliver. Now they are playing that most dangerous of games, promising one thing while doing another. The public are told that housing targets have been scrapped and that they are in control. Meanwhile, the government's planning inspectorate is instructed to allow appeals by developers and reject plans that fall short of the highest housing numbers.

Such cynicism will exact a political price. Communities are rumbling that they may not be in control at all. The coalition agreement pledged to "return decision-making powers on housing and planning to local councils". The words are in danger of ringing hollow. It would be a second political tragedy if the policy of localism produces the same contemptuous laugh as the "big society".

Giving a cowardly wink to developers won't build the houses we need. They are already sitting on 400,000 unused planning permissions, yet they choose to "land bank" to build their balance sheets rather than new homes. It's the economy, stupid, that will determine when the construction firms actually construct.

The tragedy is that the new localist approach could work. Communities that have seen random development as a threat have started to focus on what their villages and towns need, rather than on what they don't want. The earliest plans have envisioned more affordable housing, not less. Neighbourhood planning could turn people from nimbys into being part of communities that like to say yes.

But ministers are sabotaging their own policy before it's had a chance. There are enough brownfield sites for 1.5m homes, yet speculative developers are being encouraged to submit applications on open countryside regardless of emerging local plans, which carry little or no weight. Communities that have put hours of work into their plans have watched them torn up by random development, licensed by government inspectors.

And so we return to the bad old days of planning by appeal; to the ugly bolted-on housing estates; to the casual loss of countryside; to the slow, awful transformation of picturesque towns and villages into soulless commuter settlements.

None of this will help our cities. Exciting urban revivals might never have happened if developers could have made an easier buck by building boxes on green fields. Protecting the countryside isn't a selfish act or the defence of rural privilege - it's vital for city dwellers, and to retain an asset that enriches us all.

Today, the Campaign to Protect Rural England, dismayed by the random despoliation of precious landscape, launches a Save Our Countryside charter. Its president, the poet Sir Andrew Motion, calls for the defence of "our great inheritance". A laureate before him, Wordsworth, asked: "Is then no nook of English ground secure from rash assault?" The answer, if the goal of winning the global race will licence any expediency, is no.